KABC reports the TSA officer killed was a man approximately 40 years old. He died at a UCLA hospital at 11 a.m. PT. He suffered gunshot wounds to his chest and abdomen, a hospital spokesperson said. Police say he is the first TSA officer to be killed in the line of duty in the 12-year history of the agency, which was founded in the aftermath of the Sept. 11, 2001 terrorist attacks.

Police say Ciancia, 23, dressed in fatigues, was carrying a hand-written note that said he "wanted to kill TSA."

Pennsville, N.J., Police Chief Allen Cummings says Paul Ciancia's father called him saying another of his children had received a text message from the suspect "in reference to him taking his own life."

Pennsville police say they called LAPD for a welfare check. LAPD officers went to Ciancia's apartment before the airport shooting and talked to the suspect's two roommates and reported back that everything was fine.

Cummings says he told Ciancia's father that because of the son's age, he couldn't take a missing persons report. He says his department had no prior dealings with the suspect. The LAPD called Pennsville police back around the time of the LAX shooting, not knowing the identity of the LAX shooter.

Authorities say Ciancia, the lone shooter, is not a TSA employee. Police say he pulled an assault rifle out of a bag and opened fire at a screening checkpoint at 9:20 a.m. PT.

Ciancia is believed to be a white male American citizen with residences possibly in L.A. and also in New Jersey near the Delaware border.

"He proceeded into the screening area and continued shooting," said LAX Police Chief Patrick Gannon said.

LAX police located the suspect, and there was an exchange of gunfire. KABC reports he is in critical condition.

Multiple TSA employees were wounded in the shooting. Seven people were treated at the scene, and six were transported to area hospitals. Officials at Ronald Reagan UCLA Medical Center said they received three male victims: One was in critical condition, and the two others were in fair condition. One of those in fair condition was not a gunshot victim.

Although the suspect is in custody, officers were performing a sweep of Terminal 3 and surrounding areas as a precaution. The weapon used in the shooting was reportedly an AR-15 rifle.

"As you can imagine, a large amount of chaos took place in this entire incident," Gannon said.

Eric Williams was standing in the TSA line with his wife when they heard one shot, followed by multiple other shots. They ran through the TSA line, turned a corner and saw the gunman, who appeared to be walking "as if he didn't actually know where he was going."

Williams said as he and his wife ran for cover, as it appeared the shooter was going to point the gun in their direction.

"We essentially proceeded outside to the tarmac and continued to run in fear," he said.

As gunshots rang out, panicked fliers dropped to the ground. Those who had made it past security fled onto the tarmac or sought cover inside restaurants and lounges.

"We just hit the deck. Everybody in the line hit the floor and shots just continued," said Xavier Savant, who was waiting in the security line where the shooting occurred. He described it as a "Bam! Bam! Bam!" burst of gunfire.

Savant said the shots subsided and people bolted through the metal detectors and ran into the terminal, eventually making their way out to the tarmac.

"My whole thing was to get away from him," said Savant, an advertising creative director who was heading to New York with his family for a weekend trip.

Grant Imahara of the Discovery show "Mythbusters" was in an airport lounge area when he heard gunfire in the terminal and saw police and terrified passengers react. "It was fairly tense and particularly after we heard the shots ring out, like 'oh my God this is really happening,'" he said.

Gannon said actions of responding officers were heroic. "They did not hesitate, they went after this individual, they confronted this individual in our airport," Gannon says.

Ben Rosen was sitting at the Starbucks in Terminal 3 eating oatmeal at about 9:20 a.m. when he heard gunfire erupt and people start running in all directions and others crouching on the ground. Rosen got on the ground and another passenger said "don't worry we're safe."

Then more gunshots erupted. He grabbed his phone and tried to lie down as flat on the ground as he could. Police showed up with their guns drawn, shouting, "This is not a drill, hands up."

Everyone put their hands up and then were led out of the airport terminal to the international terminal, Rosen said.

As they were led out they saw broken glass from a window that looked like it'd been shot out. Rosen left his bag behind.

"It was scary I've never experienced anything like this before," he said.

The Federal Aviation Administration said a "ground stop" was in affect for all flights heading to Los Angeles, meaning planes in any other airport in the country can't take off for the city, although some flights already in the air were allowed to land.

LAX air traffic controller Michael Foote said some flights were still being allowed to depart.

Foote said his colleagues in the control tower saw passengers spilling from the terminal onto the tarmac, "evacuating the building, getting out as fast as they could." Officers eventually corralled them.

Kari Watson said she was at LAX Terminal 3 with her 3-year-old daughter moments before gunshots rang out.

"All of a sudden we heard people screaming 'Go, go, go!' and I heard a couple of pops that sounded like gunfire," she said. "People were just running, so we left everything on the ground and we took off."

Terminal 3 has been evacuated. LAPD's West Bureau and South Bureau are in a tactical alert due to the shooting.

Century Boulevard has been shut down. Motorists are advised to avoid the area, which means people trying to get to LAX by ground transportation cannot do so.

Terminal 3 is the last terminal on the north side of the airport. Airlines that operate out of the terminal include Allegiant Air, Frontier, JetBlue, Spirit and Virgin America. LAX is the third largest airport in the U.S.

In response to the LAX shooting, airports in New York are increasing their "high-visibility heavy-weapon patrol," so there is an increased display of "heavy weapons." Officials say the effort is aimed at deterring copycats.

Witness Brian Keech told The Associated Press he heard "about a dozen gunshots" from inside a security gate at the terminal, which has been evacuated.

The Federal Aviation Administration said a "ground stop" was in affect for all flights heading to Los Angeles, meaning planes in any other airports in the country can't take off for the city.

Other travelers described a chaotic scene as airport security staff evacuated terminals and rushed them outside to the tarmac. Hundreds of people remained gathered outside next to airplanes as authorities investigated what happened.

"People started saying there's a shooter, there's a shooter," said Natalie Morin, a senior at USC who was heading to San Francisco for a graduate school interview.

Los Angles is a major gateway for flights to Asia, Australia and New Zealand. The shooting occurred just before a large bank of flights arrived from Sydney, Tokyo, Beijing and other cities across the Pacific Ocean. Domestically, the largest cities served are: San Francisco, Las Vegas, New York, San Jose, Calif., San Diego and Phoenix. LAX is not a major connection point such as Chicago, Atlanta, Dallas and Minneapolis.

Most airlines issued waivers for people traveling through Los Angeles, allowing them to change flights without paying a fee. JetBlue diverted flights from Boston, New York and Fort Lauderdale, Fla. to nearby Long Beach airport. Southwest diverted at least one flight - a trip from Chicago that landed in Denver.

It was not the first shooting at LAX. On July 4, 2002, a limousine driver opened fire at the airport's El Al ticket counter, killing an airline employee and a person who was dropping off a friend at the terminal. Police killed the man.